PROJECT SUMMARY/ABSTRACT The candidate has recently been expanding his strong expertise in molecular biology of solid cancer to embrace important skills and concepts in RNA biology, hematopoiesis and leukemia, and to transition to an independent researcher. His long-term goals are to understand how lineage-control transcription factors having tumor suppressor functions are regulated in normal and malignant hematopoiesis and to exploit this understanding in modulating their expression for preventative and therapeutic purposes. The objective of his KO1 proposal is to determine how PU.1, a critical master hematopoietic transcription factor is regulated in normal and malignant hematopoiesis. PU.1 is also a key tumor suppressor in acute myeloid leukemia (AML). PU.1 expression in myeloid cells is induced by the interaction between the distal enhancer termed the upstream regulatory element (URE), and the proximal promoter region (PrPr). Reduction in PU.1 expression levels due to URE deletion has severe impacts on myeloid cell development leading to AML development. It remains unclear what regulates URE-PrPr long-range interaction. In this study, the candidate will determine the role and mechanism by which an enhancer RNA regulates PU.1 expression in normal and malignant hematopoiesis. The following specific aims will be pursued: (1) to identify that the enhancer RNA induces PU.1 expression and is important for normal hematopoiesis, (2) to define the mechanism by which it induces PU.1 expression at the chromatin level, and (3) to establish that it inhibits AML progression by restoring proper chromatin structure at the PU.1 locus thereby leading to PU.1 reactivation. Completion of these aims will provide new insights into the nuclear functions of noncoding RNAs in normal and malignant hematopoiesis, and provide a scientific basis for reactivating tumor suppressor genes by restoring proper chromatin structure. Ultimately, this could be expected to result in the development of novel molecular therapeutic approaches for AML. These aims will be achieved by using a variety of approaches including RNA interactions and gene regulation via chromatin structure with the use of transgenic, knockout and engraftment mouse models. During the award period, the candidate will focus on attaining new skills related to these proposed approaches, building his expertise and conceptual knowledge regarding gene regulation by ncRNAs in hematopoiesis and leukemia, and obtaining independent RO1-type grant. The candidate has assembled a strong mentor team. His primary mentor, Dr. Daniel Tenen, is a well-known expert in gene regulation of hematopoiesis and leukemia. In addition, the external advisor committee will monitor his research and career development progress. Furthermore, he has unparalleled access to resources and expertise at the Beth Israel Deaconess Medical Center and neighboring Harvard-affiliated institutions. Therefore, the candidate has the expertise, motivation, mentorship and academic environment necessary to successfully accomplish his proposed studies and build his independent research program.